Inland water greenhouse gas emissions offset the terrestrial carbon sink in the northern cryosphere.

Climate-sensitive northern cryosphere inland waters emit greenhouse gases (GHGs) into the atmosphere, yet their total emissions remain poorly constrained. We present a data-driven synthesis of GHG emissions from northern cryosphere inland waters considering water body types, cryosphere zones, and seasonality. We find that annual GHG emissions are dominated by carbon dioxide (1149.21307.5 1004.8 teragrams of CO2; medianQ3 Q1) and methane (14.218.5 10.1 teragrams of CH4), while the nitrous oxide emission (5.412.2 -1.4 gigagrams of N2O) is minor. The annual CO2-equivalent (CO2e) GHG emissions from northern cryosphere inland waters total 1.51.8 1.3 or 2.32.8 1.8 petagrams of CO2e using the 100-or 20-year global warming potentials, respectively. Rivers emit 64% more CO2e GHGs than lakes, despite having only one-fifth of their surface area. The continuous permafrost zone contributed half of the inland water GHG emissions. Annual CO2e emissions from northern cryosphere inland waters exceed the region's terrestrial net ecosystem exchange, highlighting the important role of inland waters in the cryospheric land-aquatic continuum under a warming climate. [ABSTRACT FROM AUTHOR]